1. Field of The Invention
The present invention relates to a heat sink, and particularly to a heat sink having a removable protective cap for enclosing thermal grease on the heat sink, thereby protecting the thermal grease from contamination before the heat sink is assembled to a CPU/CPU module.
2. The Prior Art
Following the increase in consumed power of CPUs, heat sinks made by aluminum extrusion or folded fins are popularly used to dissipate heat generated by the CPUs. The heat sinks disclosed in U.S. Pat. Nos. 5,019,940, 5,276,585, 5,486,981, 5,590,025 and 5,594,624 directly contact a CPU.
Referring to FIG. 1, a CPU and other auxiliary components (not shown) are received in a CPU module 1 which has a metallic mounting plate 12 contacting the CPU and defines a number of holes 122 for extension of a mounting device (not shown) therethrough to fixedly attach a heat sink 3 to the CPU module 1. To improve heat conductivity between the heat sink 3 and the mounting plate 12, thermal interface material 2 is applied to a bottom face 310 of the heat sink 3. The heat from the CPU causes the thermal interface material 2 to become viscous thereby filling the air gap between the heat sink 3 and the mounting plate 12. The thermal interface material 2 can be thermal tape or thermal grease. A strip of thermal tape applied to the bottom face 310 of the heat sink 3 in advance will not contaminate surrounding articles or be contaminated by dust or foreign particles during transportation/handling of the heat sink 3 since it is solid at ambient temperature. Thermal grease cannot be applied to the heat sink 3 in advance since it is not solid at ambient temperature and may contaminate surrounding articles or be contaminated by dust or foreign particles before the heat sink 3 is assembled to the CPU module 1. Conventionally, the thermal grease is applied to the heat sink 1 just prior to assembly with the CPU module 1. Such an operation extends the assembly time of the heat sink 3 and the CPU module 1.
Although thermal tape is more convenient to use, it has a higher viscosity when heated; therefore, it can not improve the heat conductivity of the heat sink as well as thermal grease. Hence, an improvement is needed so that the thermal grease can be applied to the heat sink in advance without contaminating surrounding articles or being contaminated by dust or foreign particles during transportation or handling of the heat sink.